Hi JR, and welcome to the Forum.
Two things spring to mind about why your hens might be losing weight. Firstly, a diet of mixed corn and kitchen scraps will not give them the balanced nutrition they need, especially in very cold weather, and at a time of year when the longer days may mean they are coming back into lay. Keeping warm and laying eggs put a big strain on the chickens' resources, and they need a diet higher in protein than mixed corn, which has about 10% i think. Kittchen scraps are usually useless nutritionally for hens, although they do like them they count as 'junk food' generally and should be avoided altogether, or only fed occasionally in very small quantities as a treat. You can give fresh trimmings from greens such as cabbage or cauliflower, and small quantities of fruit etc, but yuo should completely avoid anything like bread, cakes or other cooked leftovers containing fat, salt or sugar. Most people feed layers pellets or layers mash to adult hens, and a good brand will contain the full spectrum of nutrients, vitamins and minerals they need, including calcium for eggshell production and about 15% protein.
The other thing you might think about is worms. If your hens haven't been wormed with Flubenvet in the past 4-6 months, they may well be carrying a heavy worm burden, which will lead to loss of weight and condition as the worms take nourishment from the food in the hens' guts. All hens get worms from foraging and from eating earthworms and slugs which are hosts to the sorts of worms that affect chickens. The most reliable and easily obtained wormer for hens is Flubenvet, given in their food as a 7-day course. You can find more about Flubenvet in the Chickens Health section here http://bit.ly/yZVKpd there are some other herbal preparations on the market which may be helpful as tonics for the chickens, but they are not effective at dealing with an established worm burden.
